1. Field of the Art
The present invention relates to Ziegler polymerization of .alpha.-olefins. More particularly, the present invention is concerned with Ziegler polymerization of .alpha.-olefins characterized by, among others, the solid catalyst components comprising a transition metal in Ziegler-type catalysts.
Use of the solid catalyst component in accordance with the present invention in Ziegler-type catalysts as the transition metal component will make it possible to produce polymers endowed with improved stereoregularity with less amount of polymer by-products in a higher yield.
2. Background of the invention
Although the catalysts heretofore proposed for the polymerization of olefins comprising a solid catalyst component containing titanium, magnesium and a halogen as the essential ingredients and an organoaluminum have shown extremely high activity, yet it has been necessary to use an electron donative compound (electron donor) during polymerization, when the high stereoregularity of polymer products is desired.
However, problems with such catalysts using the electron donative compound as the third component (outside donor) are that difficulties are encountered in the control of the performance of polymer products inclusive of the regulation of their molecular weight for reasons that the velocity of polymerization drops due to the reaction of the organoaluminum compound with the electron donative compound, when the polymerization temperature is elevated so as to increase the velocity of polymerization, which reaction is so accelerated that an attempt to increase the yield (or productivity) of polymers by doing so is subject to restriction. Furthermore, considerable amount of the electron donative compound is required for obtaining stereoregularity at a high level desired, and the polymers thereby produced have smell due to the electron donative compound used and contained in the polymer when conventional catalyst-removal processing is omitted.
Therefore, it is now desired to develop catalyst systems which overcome the aforesaid problems and make it possible to produce highly stereoregular polymers with improved catalytic yields but without using any electron donative compound as the third component, i.e. what is called "outside electron donor".